DOE OSTI2020
MgYb2S4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded to five S2- atoms to form MgS5 square pyramids that share corners with two equivalent YbS6 octahedra, corners with four equivalent YbS5 trigonal bipyramids, an edgeedge with one YbS6 octahedra, edges with four equivalent MgS5 square pyramids, and an edgeedge with one YbS5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 23°. There are a spread of Mg–S bond distances ranging from 2.47–2.72 Å. There are two inequivalent Yb3+ sites. In the first Yb3+ site, Yb3+ is bonded to six S2- atoms to form YbS6 octahedra that share corners with two equivalent MgS5 square pyramids, a cornercorner with one SYb2Mg2S trigonal bipyramid, corners with five equivalent YbS5 trigonal bipyramids, edges with four equivalent YbS6 octahedra, and an edgeedge with one MgS5 square pyramid. There are a spread of Yb–S bond distances ranging from 2.63–3.31 Å. In the second Yb3+ site, Yb3+ is bonded to five S2- atoms to form YbS5 trigonal bipyramids that share corners with five equivalent YbS6 octahedra, corners with four equivalent MgS5 square pyramids, corners with two equivalent SYb2Mg2S trigonal bipyramids, an edgeedge with one MgS5 square pyramid, and edges with two equivalent YbS5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 52–82°. There are a spread of Yb–S bond distances ranging from 2.59–2.81 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to three equivalent Mg2+ and two equivalent Yb3+ atoms to form distorted SYb2Mg3 trigonal bipyramids that share corners with four equivalent SYb2Mg2S trigonal bipyramids, corners with two equivalent SYb4 trigonal pyramids, and edges with five SYb2Mg2S trigonal bipyramids. In the second S2- site, S2- is bonded to four Yb3+ atoms to form SYb4 trigonal pyramids that share corners with six SYb2Mg2S trigonal bipyramids, corners with two equivalent SYb4 trigonal pyramids, an edgeedge with one SYb2Mg2S trigonal bipyramid, and edges with two equivalent SYb4 trigonal pyramids. In the third S2- site, S2- is bonded in a 4-coordinate geometry to three Yb3+ and one S2- atom. The S–S bond length is 2.14 Å. In the fourth S2- site, S2- is bonded to two equivalent Mg2+, two equivalent Yb3+, and one S2- atom to form distorted SYb2Mg2S trigonal bipyramids that share a cornercorner with one YbS6 octahedra, corners with two equivalent YbS5 trigonal bipyramids, corners with four equivalent SYb2Mg3 trigonal bipyramids, corners with four equivalent SYb4 trigonal pyramids, edges with three SYb2Mg2S trigonal bipyramids, and an edgeedge with one SYb4 trigonal pyramid. The corner-sharing octahedral tilt angles are 34°.